Often people spend a great deal of time seated each day, whether it be in an office chair, in a car, in a truck, or riding a motorcycle. Often, the seats have virtually no way of being adjusted so that they can be made more comfortable to a person sitting in the seat. As a result, seats with little or no adjustability can be very uncomfortable to sit in, particularly for long periods of time. Additionally, such seating can contribute to fatigue or can improperly support body parts of the person sitting in the seat, such as, for example, resulting in poor lumbar support to the lower back of the seat occupant, which can undesirably increase fatigue by making the body part sore or stiff. Moreover, lack of adjustability can result in a seat occupant being poorly positioned relative to another object, such as the steering wheel of an automobile or the handlebars of a motorcycle. Finally, since people come in many different shapes, sizes, and weights, a seat lacking adequate adjustability may not properly fit a particular type or size of person, also making it very uncomfortable for that person to remain seated for long periods of time without experiencing discomfort or fatigue.
In light of all of these difficulties, seating designers have attempted to design seats which are adjustable in many different ways to improve comfort, decrease fatigue, properly position the seat occupant, and comfortably fit people of a wide variety of sizes, shapes and weights. However, seat design can be very complicated, particularly for vehicle seating designers. For example, it is known by vehicle seat designers that comfort to a seat occupant can be extremely important to the safety of the seat occupant. Therefore, vehicle seat designers attempt to design seats such that occupants having different body dimensions do not suffer driving fatigue, which can be detrimental to safety.
There are other factors that a seat designer must contend with as well. For example, it is desirable that a vehicle seat provide proper support to individual body areas by controlling how the pressure of the seat against a seat occupant is distributed. Additionally, it is preferred that a seat provide adequate lateral support to a seat occupant when the vehicle is turning while enabling the occupant to relatively freely adjust their sitting position without needing to readjust the seat.
Moreover, the components responsible for enabling seat adjustment must not adversely affect the vibrational and damping characteristics of the seat by preventing the natural frequency of the seat from falling within a range of excitation frequencies that are likely to be encountered during operation. Therefore, the distribution of the spring rates in the areas of the seat cushion and backrest where the adjustable components are located, as well as the overall spring rate and dampening capacity of the seat, must not be adversely affected by the use and operation of the adjustable components. Finally, all of the components which enable seat adjustability must be conveniently packaged within the seat while also not undesirably affecting the appearance of the seat.
To enhance seat occupant comfort, overlays or cushions have been developed that have one or more inflatable chambers. One such seat overlay, in the form of a seat cushion, is disclosed in Wilson, U.S. Pat. No. 3,540,776. These overlays are typically placed over a seat and inflated before the seat occupant sits down to enhance the comfort of the seat occupant. Unfortunately, these overlays are not specifically designed to maximize comfort for a specific seat contour but rather are designed to be used with any type of seat. As a result, these overlays can be more effective at preventing discomfort and fatigue when used with some types of seats and not with other types of seats.
Moreover, these overlay cushions are not particularly well suited for use in automotive vehicles because they can slip and slide around making them difficult to properly position for maximum comfort and because they can be easily damaged during use. Additionally, these overlays typically must be manually inflated and will leak over time, undesirably requiring periodic and time consuming manual reinflation.
Finally, the amount of cushioning provided by such an overlay is also limited because each chamber typically has a generally rounded "pillow" shaped construction which limits the inflated volume of the chamber thereby also limiting how deeply each chamber can be compressed during cushioning a seat occupant during use and operation of the overlay. To achieve greater cushioning, the surface area of a "pillow" shaped inflatable chamber can be increased to enable it to expand outwardly a greater distance when fully inflated. Unfortunately, such a larger, "pillow" shaped inflatable chamber requires a greater volume of air to inflate, which can be time consuming. Additionally, a "pillow" shaped chamber may not always uniformly apply pressure to the desired body part of the seat occupant thereby possibly reducing the amount of comfort that can be achieved.
The use of an air bladder having such a "pillow" inflatable chamber construction is less desirable for use with motorcycle seats because their seats are smaller, reducing the amount of cushioning that a "pillow" shaped inflatable chamber can provide because of the limited surface area available on the motorcycle seat limiting its maximum inflatable volume. Finally, it is virtually impossible to produce an inflatable overlay or bladder with individual inflatable chambers having the "pillow" construction because of the limited surface area reducing the surface area available for each chamber limiting the maximum cushioning available for a multi-chamber motorcycle seat overlay or built in inflatable bladder.
In other instances, inflatable bladders that are built into the seat have been used to provide adjustment to increase comfort and reduce fatigue. Examples of such built-in bladders are found in Flajole, U.S. Pat. No. 2,938,570, Isono et al., U.S. Pat. No. 4,592,588, and Ishida, et al., U.S. Pat. No. 4,807,931. These types of bladders cannot be easily manually inflated and typically require some source of air, such as from a hand bulb pump or another type of pressurized air supply, to inflate the bladder. For bladders which have more than one inflatable chamber, rather elaborate and complicated valving and air distribution arrangements have been developed, the assembly and installation of which are not cost effective particularly in light of the competitive economic climate that exists today in the automotive and off-road vehicle industries.
For example, Isono, et al., U.S. Pat. No. 4,592,588 discloses a vehicle seat having separate independently inflatable bladders received in compartments within the seat and underneath the seat cover. Unfortunately, each bladder is of separate and independent construction from every other bladder and requires separate insertion of each bladder into its compartment during assembly undesirably increasing the number of assembly steps as well as the cost to assemble a vehicle seat of the disclosed construction. Moreover, as a result of each bladder being independent of every other bladder, conduit or piping must be attached to each bladder and manually routed to an air supply which can even further undesirably increase assembly costs.